Post Irradiation Examination of MEGAPIE – How radiochemical analytics helps looking inside a high-power liquid metal spallation target
For the radioanalytical work, the colleagues of the Hotlaboratory (AHL) of PSI extracted more than 70 samples from representative positions within the target, comprising bulk LBE, samples from the interfaces between the vessel walls and the LBE as well as the cover gas and the LBE.
The radiochemists at PSI could not only identify and quantify 20 radionuclides using α- and γ- spectrometric methods at PSI and accelerator mass spectrometry (AMS) at ETH Zurich, but also investigated their spatial distribution within the target. They found that radionuclides do not necessarily remain dissolved in the irradiated LBE. Instead they tend to accumulate on surfaces, and therefore have depleted abundance in the bulk LBE. The unequal distribution appears to be more pronounced for strongly electropositive metals (133Ba, 173Lu, 172Hf/Lu, 60Co, 148Gd) and less or completely absent for nobler metals (101,102Rh and 110mAg), respectively. These findings have a high impact on the safety assessment of nuclear installations, especially concerning dose rate estimations and the evaluation of structure material damage.
Theoretical predictions of the radionuclide inventory performed in collaboration with colleagues from CEA/Saclay and ESSS Lund, based on calculation codes and models like INCL/ABLA, MCNPX or FLUKA, mostly agreed well or at least fairly with the experimental values. However, in several cases considerable discrepancies were found. The knowledge on the actual radionuclide production rates serves as benchmark and helps to improve the codes and models.
Additional informationEPJ Plus Highlight – Improving safety of neutron sources
ContactDr. Dorothea Schumann
Radwaste Analytics Group
Laboratory for Radiochemistry (LRC)
Paul Scherrer Institut
Telephone: +41 56 310 4004
Original PublicationDistribution and Surface Enrichment of Radionuclides in Lead-Bismuth Eutectic from Spallation Targets
B. Hammer-Rotzler, J. Neuhausen, V. Boutellier, M. Wohlmuther, L. Zanini, J.-C. David, A. Türler, D. Schumann
Eur. Phys. J. Plus 15 July 2016: Vol. 131, pp. 233